A reference handbook of the medical sciences, embracing the entire range of scientific and practical medicine and allied science . Fig. —Egg of ScylliumCanicula. The lif^hter area isthe blastoderm resting upon theilarker yolk. The medullary marginal fold is transitory, disappearing at an earlystage, after which the whole p(^ri])hiry of tlie blasto-derm consists of a zone of overgrowtli (Fig. 660),which advances over the yolk and finally i^ embryo arises near the center of the blastodermin connection with the primitive streak, which isdescribed with the other structures of th
A reference handbook of the medical sciences, embracing the entire range of scientific and practical medicine and allied science . Fig. —Egg of ScylliumCanicula. The lif^hter area isthe blastoderm resting upon theilarker yolk. The medullary marginal fold is transitory, disappearing at an earlystage, after which the whole p(^ri])hiry of tlie blasto-derm consists of a zone of overgrowtli (Fig. 660),which advances over the yolk and finally i^ embryo arises near the center of the blastodermin connection with the primitive streak, which isdescribed with the other structures of the blastodermin another article. (See Area Emhryonalis.) The blastoderm of the Gymnophiona shows somevery interesting features intermediate in structurelietween tlie two main Fio. —Transverse Section through the Center of the Blas-toilerm of a Pigeons Egg taken Fourteen and One-half Hoursafter Fertilization, p. Periblast, (.\fter Blount.) In the mammals, there are three types of eggscorresponding to the three main divisions of the group. The egg of the monotremes resembles a reptUesegg except in size. When the egg enters the oviduct to 4 millimeters in diameter, which would be verysmall for a reptile of the same size as the mother,but much larger than other mammalian eggs. It isladen with both white and yellow yolk, consisting ofdiscrete yolk-spheres and is surrounded by a vitellinemembrane. In the oviduct it receives additionalenvelopes, a layer of albumen and a horny still covered by the shell the egg is laid andreceived into the mammary pouch where it in the uterus, development proceeds, so thatwhen the egg is laid the embryo of Ornithorhynchus
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Keywords: ., bookauthorbuckalbe, bookcentury1900, bookdecade1910, bookyear1913
